By Julie Boudreau
When you are in the least interested in alpine plants, you inevitably discover troughs. These thick concrete containers have become, for reasons still unexplained to this day, the containers of choice for perfecting the art of growing alpine plants. However, I also see in these wonderful pots an untapped potential for balcony gardening.
A Bit of History
Where did this idea come from? To cultivate the small and delicate alpine plants in these massive containers that are troughs? There is nothing refined in the trough itself. It is a more or less deep container, entirely made of concrete (a special kind of concrete, as we will see later). The walls are thick and, let’s face it, they weigh a ton!
Like many horticultural passions, interest in alpine plants originated in England. As early as 1760, wealthy and noble Britons experimented with the idea of growing alpine plants in their gardens. With more or less success! It is almost 100 years later that the gardeners avid of mountain plants will develop a whole expertise, both in the construction of “arrangements of rocks” and in the composition of suitable substrates.
The exact origins of the use of troughs remain unknown, but we can attribute their enthusiasm to a certain Clarence Elliott, in 1923. The previous year, this horticultural columnist and owner of the Six Hills Nursery had visited Mrs. Saunders at Wennington Hall in Lancashire. She cultivated rare plants in these famous troughs. The following year, at the famous Chelsea Flower Show, Elliott presented an alpine garden made up of rock mounds and various troughs. The trend was launched!
Originally, troughs were drinking containers for cattle. First sculpted in natural stone, troughs were then made of concrete. They were big and imposing (and very heavy). It can be argued that the modernization of farms has rendered them obsolete. Thus, in the 1920s, they were unearthed behind barns and farmers were freed from their burdens, for a low cost! Their popularity was instantaneous, and by 1925 real troughs had become rare and expensive.
It was then that we became interested in their fabrication. Indeed, the concrete mixture of troughs is not a standard concrete. It is made of peat moss. In general, the recipe is one part cement, one part coarse sand and one or two parts peat moss. One day, during a lecture I gave in a horticultural society, a man in the room came to explain to me all the chemistry of concrete! He was a retired engineer. This is where I learned that peat moss gives concrete elasticity!
The Advantages of Trough Culture
Indeed, this is the great beauty of troughs: they can remain outside without protection for years without ever cracking. The same cannot be said for terracotta or ceramic containers. The concrete of the troughs, commonly called hypertufa, is resistant… and elastic!
Now most alpine plant enthusiasts make their own hypertufa troughs. The formats are smaller, which facilitates handling, and drainage holes are provided. Because, in the case of the original troughs, you had to manually make drainage holes to evacuate any excess water.
Being a container of limited space, the trough allows plants to be grown in collections, to adapt the growing medium to certain requirements. For example, a more calcareous substrate can be created to suit plants that like high pH.
But the beauty of troughs is that the plants grown there can overwinter in their container. Even in northern North America!
Of course, you have to choose your plants carefully, but overwintering the troughs is quite simple: when autumn arrives, the troughs are simply placed on the ground (if they are raised) and placed where the snow accumulates. No protection, no transplanting the plants in the ground. Leave it all as it is.
The Trough, for the Urban Gardener?
And it is here that the trough becomes a potentially interesting niche for the urban gardener. It is therefore more than possible to cultivate a collection of alpine plants in troughs, on a balcony! Even better, the trough can simply become a decorative container in which to grow any perennial plant. Why not an edible garden, made up of chives, rhubarb, blackcurrant and sorrel! All of these plants do well in raised containers. Why not in a trough?